1 Introduction to Vegetable Grafting
ZHILONG BIE,1* MUHAMMAD AZHER NAWAZ,1,2 YUAN HUANG,1 JUNG-MYUNG LEE3 AND GIUSEPPE COLLA4
1Huazhong Agricultural University/Key Laboratory of Horticultural Plant Biology, Wuhan, PR China; 2Department of Horticulture, University College of Agriculture, University of Sargodha, Sargodha, Pakistan; 3formerly of Kyung Hee University, Seoul, Republic of Korea; 4University of Tuscia, Viterbo, Italy
1.1 Importance and Use of Vegetable Grafting
1.1.1 Historical perspective
Grafting is the art of joining together two plant parts (a rootstock and a scion) by means of tissue regeneration, in which the resulting combination of plant parts achieves physical reunion and grows as a single plant (Janick, 1986). It is a centuries-old technique but a relatively new one in vegetable cultivation. Various references to fruit grafting appear in the Bible and in ancient Greek and Chinese literature, suggesting that grafting was used in Europe, the Middle East and Asia by the 5th century BC (Melnyk and Meyerowitz, 2015). Grafting occurs commonly in nature, and the observation of natural grafts may have inspired human use of this technique in horticulture thousands of years ago (Mudge et al., 2009).
Grafting of fruit trees has been practised for thousands of years, but in vegetables this technique is a relatively new one. Self-grafting was used as a technique to produce large-sized gourd fruits, as reported in a Chinese book written in the 5th century and a Korean book written in the 17th century (Lee and Oda, 2003). However, commercial grafting of vegetables only originated in the early 20th century with the aim of managing soilborne pathogens (Louws et al., 2010).
Scientific vegetable grafting was first launched in Japan and Korea in the late 1920s by grafting watermelon on to gourd rootstocks to avoid soilborne diseases (Ashita, 1927; Yamakawa, 1983). This new technique was disseminated to farmers in Japan and Korea by the agricultural extension workers. In the early 1930s, the commercial use of grafted transplants was started in Japan by grafting watermelon on to bottle gourd (Lagenaria siceraria (Mol.) Standl) and summer squash (Cucurbita moschata Duch.) to induce resistance to Fusarium wilt (Oda, 2002; Sakata et al., 2007, 2008). Grafting of cucumber to reduce soilborne diseases and to enhance scion vigour is believed to have started in the 1920s but was not applied on a commercial scale until the 1960s (Sakata et al., 2008).
Among the Solanaceae crops, aubergine (Solanum melongena L.) was first grafted on to scarlet aubergine (Solanum integrifolium Lam.) in the 1950s (Oda, 1999). Similarly, grafting of tomato (Solanum lycopersicum L.) was started in the 1960s (Lee and Oda, 2003). In the 1950s, the rapid development of protected cultivation with the use of greenhouses or tunnels for offseason vegetable production and intensive cropping patterns changed the existing crop rotation system; consequently, farmers became dependent on grafting to control soilborne pathogens and other pests (Kubota et al., 2008; Lee et al., 2010).
Scientific studies investigating and developing rootstocks was initiated in the 1960s in Korea. By 1990, the percentage of grafted Solanaceae and Cucurbitaceae (e.g. cucumber, melon, aubergine, tomato) had increased to 59% in Japan and 81% in Korea (Lee, 1994). Currently, most greenhouse-cultivated cucurbits are grafted in China, Japan, Korea, Turkey and Israel, while grafted vegetables are cultivated on a commercial scale in more than 20 countries worldwide (Table 1.1).
Table 1.1. Main countries where grafted vegetables are produced and/or cultivated on a commercial scale.
Continent | Countries |
East Asia | China, Japan, Korea, the Philippines |
Europe | Spain, Italy, the Netherlands, France, Greece, Cyprus, Belgium, Portugal, Germany, Croatia, Bosnia and Herzegovina |
Middle East and North Africa | Turkey, Israel, Morocco, Egypt, Iran, Algeria |
Americas | Mexico, Canada, the USA, Argentina |
1.1.2 Purpose and scope
Although vegetable grafting in ancient times was intended mainly to produce large-sized gourds for rice storage (Hong, 1710; PSNCK, 1982), it expanded rapidly in many countries to control soilborne pathogens (e.g. root-knot nematodes) and foliar pathogens, to enhance plant vigour, to extend the harvesting period, to increase yield and fruit quality, to prolong postharvest life, to increase nutrient uptake, to allow tolerance to low and high temperatures, to cope with salinity and heavy-metal stress, and to increase tolerance to drought and waterlogging (Table 1.2; see Chapters 6 and 7, this volume).
Table 1.2. Benefits of vegetables grafting.
Benefit | Crop | Reference |
Disease resistance to soilborne pathogens and foliar pathogens | Tomato, watermelon, aubergine, artichoke, cucumber, pepper, melon | Black et al. (2003); Bletsos et al. (2003); Bletsos (2005, 2006); Sakata et al. (2006, 2007, 2008); King et al. (2008); Lee et al. (2010); Louws et al. (2010); Kousik et al. (2012); Jang et al. (2012); Temperini et al. (2013); Gilardi et al. (2013a,b); Vitale et al. (2014); Arwiyanto et al. (2015); Miles et al. (2015); Shibuya et al. (2015); Suchoff et al. (2015) |
Nematode resistance | Tomato | Dong et al. (2007); Lee et al. (2010); Louws et al. (2010) |
Salt tolerance | Cucumber, pepper, watermelon, tomato | Huang et al. (2009); Colla et al. (2010, 2012, 2013); Huang et al. (2010, 2013a); Lee et al. (2010); Schwarz et al. (2010); Fan et al. (2011); Yang et al. (2012, 2013); Wahb-Allah (2014); Penella et al. (2015); Xing et al. (2015) |
High- and low-temperature tolerance | Tomato, pepper, cucumber | Venema et al. (2008); Li et al. (2008); Lee et al. (2010); Schwarz et al. (2010); López-Marín et al. (2013) |
Drought tolerance | Pepper, tomato | Lee et al. (2010); Schwarz et al. (2010); Penella et al. (2014); Wahb-Allah (2014) |
Flooding tolerance | Tomato | Lee et al. (2010); Bhatt et al. (2015) |
Nutrient uptake | Watermelon, tomato, melon | Kim and Lee (1989); Ruiz et al. (1997); Lee et al. (2010); Colla et al. (2010b, 2011); Huang et al. (2013b, 2016a,b); Schwarz et al. (2013); Huang et al. (2016a,b); Nawaz et al. (2016) |
Yield increase | Watermelon, melon cucumber, tomato, aubergine, pepper, artichoke | Jeong (1986); Ruiz et al. (1997); Nisini et al. (2002); Colla et al. (2008); Huang et al. (2009); Lee et al. (2010); Gisbert et al. (2011); Moncada et al. (2013); Tsaballa et al. (2013); Temperini et al. (2013) |
Fruit quality improvement | Tomato, cucumber, aubergine, pepper, melon, watermelon | Jeong (1986); Proietti et al. (2008); Huang et al. (2009); Lee et al. (2010); Rouphael et al. (2010); Gisbert et al. (2011); Zhao et al. (2011); Condurso et al. (2012); Krumbein and Schwarz (2013); Moncada et al. (2013); Tsaballa et al. (2013); Verzera et al. (2014); Kyriacou et al. (2016) |
Scion vigour improvement | Cucumber | Jeong (1986); Lee et al. (2010) |
Reproductive growth promotion | Cucumber | Jeong (1986); Lee et al. (2010) |
Shelf-life/postharvest life improvement | Melon | Zhao et al. (2011) |
Heavy metals/organic pollutants tolerance | Cucumber, tomato | Rouphael et al. (2008); Lee et al. (2010); Schwarz et al. (2010); Zhang et al. (2010a,b, 2013); Kumar et al. (2015a,b) |
Extension of harvesting period | Cucumber | Jeong (1986); Itagi (1992); Ito (1992); Lee et al. (2010) |
Weed control/management | – | Dor et al. (2010 ); Louws et al. (2010) |
Production of new species (tetraploid) | Tobacco | Fuentes et al. (2014) |
As well as myriad applications in advancing sustainable crop production, grafting can be used as a tool in both breeding and research. Recently, a group of researchers from Germany working on tobacco published a unique way of producing new allohexaploid tobacco species by using the graft site as propagation material in vitro (Fuentes et al., 2014); in this case, grafting can be seen as a breeding tool to generate novel genetic combinations – in a process that is conceptually similar to protoplast fusion – by hybridization at the cellular level, bypassing sexual compatibility barriers (see Chapter 3, this volume). Independent breedi...